Lithium-ion secondary batteries have positive and negative electrodes that can reversibly absorb and desorb lithium ions, and an electrolyte interposed between the both electrodes. Charging and discharging is accomplished by the back-and-forth movement of the lithium ions in the electrolyte between the both electrodes. Lithium-ion secondary batteries are used as a power source in various kinds of portable devices because they are lightweight and have a high energy density. Moreover, the use of lithium-ion secondary batteries has been studied in fields that require large capacity power sources such as hybrid automobiles, electric automobiles, and the like where even greater improvement in battery performance is needed. More specifically, excellent high-temperature storage characteristics are important in lithium-ion secondary batteries intended for application in automobiles or others in which environment temperature or storage temperature can be high. Patent Documents 1 to 3 can be noted as technical documents relating to the high-temperature storage characteristics of batteries.    Patent Document 1: Japanese Patent Application Laid-open No. 2003-151623    Patent Document 2: Japanese Patent Application Laid-open No. 2002-359002    Patent Document 3: Japanese Patent Application Laid-open No. 2007-134047